1. Field of the Invention
The present invention relates to a measuring apparatus which measures the shape of an object, and a method of manufacturing an article.
2. Description of the Related Art
As a method of measuring the shape of an object using light in a noncontact manner, a pattern projection method (pattern projection triangulation) is known. The pattern projection method is a method of obtaining the shape of an object to be measured by sensing an image of the object to which a known two-dimensional pattern has been projected, and detecting the deformation amount of the two-dimensional pattern generated in accordance with the shape of the object.
In general, a measuring apparatus using the pattern projection method individually includes a projection optical system for projecting pattern light to an object to be measured, and an imaging optical system for sensing an image of the object irradiated with the pattern light. To measure the shape of an object at high accuracy in the measuring apparatus using the pattern projection method, it is effective to constitute the projection optical system and imaging optical system as telecentric optical systems.
Japanese Patent Laid-Open No. 2013-178174 has disclosed a method of enlarging a measurement range by exploiting the difference in the phase period of a grating pattern image to be sensed using a whole-space tabulation method.
The measuring apparatus using the pattern projection method desirably has a wide field of view and a wide measurement range in the direction of height in order to improve the throughput. To achieve both the wide field of view and the wide measurement range, measures such as widening of the field of view of the projection optical system or imaging optical system, and decreasing of the the convergence angle are conceivable. However, to widen the field of view of the optical system, the size of the optical system needs to be increased because the optical system is telecentric. This increases the apparatus size and apparatus cost. If the convergence angle is decreased, the working distance may need to be prolonged in order to avoid physical interference between the projection optical system and the imaging optical system. This may upsize the measuring apparatus.
The method disclosed in Japanese Patent Laid-Open No. 2013-178174 requires a high-accuracy driving mechanism of finely driving an object to be measured in the direction of height. This complicates the apparatus and raises the apparatus cost. Since the object needs to be measured while finely driving it, a long measurement time is taken.